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Hiʻiaka was the first satellite discovered around Haumea. It is named after one of the daughters of Haumea, Hiʻiaka, the patron goddess of the Big Island of Hawaii, though at first it had gone by the nickname "Rudolph" by its discovery team. It orbits once every 7006424396800000000♠49.12±0.03 d at a distance of 7007498800000000000♠49880±198km, with an eccentricity of 6998513000000000000♠0.0513±0.0078 and an inclination of 7002126356000000000♠126.356±0.064°. Mutual events expected in July 2009 should improve the knowledge of the orbits and masses of the components of the Haumean system.[2]

Its measured brightness is 7000590000000000000♠5.9±0.5%, translating into a diameter of about 22% of its primary, or in the range of 7005320000000000000♠320 km, assuming similar albedo.[2] To put this in perspective, this would make it larger than all but four of the asteroids, after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea. Future exploration of Haumea and its moons could reveal that Hiʻiaka is in hydrostatic equilibrium, i.e. rounded by its own gravity. However, it is not a dwarf-planet candidate because it is a moon.

The near infrared spectrum of Hiʻiaka is dominated by water-ice absorption bands, which means that its surface is made mainly of water ice. The presence of the band centered at 6994165009999900000♠1.65 µm indicates that the surface water ice is primarily in the crystalline form. Currently it is unclear why water ice on the surface has not turned into amorphous form as would be expected due to its constant irradiation by cosmic rays.[3]